<template>
  <div class="spec-preview">
    <img :src="imgObj.imgUrl" />
    <div class="event" @mousemove="changeMaskOffset" ref="img"></div>
    <div class="big">
      <img :src="imgObj.imgUrl" ref="bigImg"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props:['zoomList'],
    data() {
      return {
        currentIndex:0,
      }
    },
    computed: {
      imgObj(){
        return this.zoomList[this.currentIndex] || {};
      }
    },
    methods: {
      getImgIndex(index){
        this.currentIndex = index;
      },
      changeMaskOffset(e){
        let mask = this.$refs.mask;
        let img = this.$refs.img;
        let bigImg = this.$refs.bigImg;
        let smallToBig = bigImg.offsetWidth / img.offsetWidth;
        let leftMax = img.offsetWidth-mask.offsetHeight;
        let topMax = img.offsetHeight-mask.offsetHeight;
        let left = e.offsetX - mask.offsetWidth/2;
        let top = e.offsetY - mask.offsetHeight/2;
        left = left < 0 ? 0 : left;
        left = left > leftMax ? leftMax : left;
        top = top < 0 ? 0 : top;
        top = top > topMax ? topMax : top;
        // 设置遮罩层
        mask.style.left = left + 'px';
        mask.style.top = top + 'px';
        // 设置大图
        bigImg.style.left = -(left * smallToBig) + 'px';
        bigImg.style.top = -(top * smallToBig) + 'px';
      }
    },
    mounted () {
      this.$bus.$on('getImgIndex',this.getImgIndex);
    },
    beforeDestroy(){
      this.$bus.$off('getImgIndex');
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>